#pragma once

#include <uapi/cdefs.h>

/*
 * This file defines five types of data structures: singly-linked lists,
 * lists, simple queues, tail queues, and circular queues.
 *
 * A singly-linked list is headed by a single forward pointer. The
 * elements are singly linked for minimum space and pointer manipulation
 * overhead at the expense of O(n) removal for arbitrary elements. New
 * elements can be added to the list after an existing element or at the
 * head of the list.  Elements being removed from the head of the list
 * should use the explicit macro for this purpose for optimum
 * efficiency. A singly-linked list may only be traversed in the forward
 * direction.  Singly-linked lists are ideal for applications with large
 * datasets and few or no removals or for implementing a LIFO queue.
 *
 * A list is headed by a single forward pointer (or an array of forward
 * pointers for a hash table header). The elements are doubly linked
 * so that an arbitrary element can be removed without a need to
 * traverse the list. New elements can be added to the list before
 * or after an existing element or at the head of the list. A list
 * may only be traversed in the forward direction.
 *
 * A simple queue is headed by a pair of pointers, one the head of the
 * list and the other to the tail of the list. The elements are singly
 * linked to save space, so elements can only be removed from the
 * head of the list. New elements can be added to the list after
 * an existing element, at the head of the list, or at the end of the
 * list. A simple queue may only be traversed in the forward direction.
 *
 * A tail queue is headed by a pair of pointers, one to the head of the
 * list and the other to the tail of the list. The elements are doubly
 * linked so that an arbitrary element can be removed without a need to
 * traverse the list. New elements can be added to the list before or
 * after an existing element, at the head of the list, or at the end of
 * the list. A tail queue may be traversed in either direction.
 *
 * A circle queue is headed by a pair of pointers, one to the head of the
 * list and the other to the tail of the list. The elements are doubly
 * linked so that an arbitrary element can be removed without a need to
 * traverse the list. New elements can be added to the list before or after
 * an existing element, at the head of the list, or at the end of the list.
 * A circle queue may be traversed in either direction, but has a more
 * complex end of list detection.
 *
 * For details on the use of these macros, see the queue(3) manual page.
 */

/*
 * Include the definition of NULL only on NetBSD because sys/null.h
 * is not available elsewhere.  This conditional makes the header
 * portable and it can simply be dropped verbatim into any system.
 * The caveat is that on other systems some other header
 * must provide NULL before the macros can be used.
 */
#ifdef __NetBSD__
#include <sys/null.h>
#endif

#if defined(QUEUEDEBUG)
#if defined(_KERNEL)
#define QUEUEDEBUG_ABORT(...) panic(__VA_ARGS__)
#else
#include <err.h>
#define QUEUEDEBUG_ABORT(...) err(1, __VA_ARGS__)
#endif
#endif

/*
 * Singly-linked List definitions.
 */
#define SLIST_HEAD(name, type)                                                                     \
    struct name {                                                                                  \
        struct type *slh_first; /* first element */                                                \
    }

#define SLIST_HEAD_INITIALIZER(head)                                                               \
    {                                                                                              \
        NULL                                                                                       \
    }

#define SLIST_ENTRY(type)                                                                          \
    struct {                                                                                       \
        struct type *sle_next; /* next element */                                                  \
    }

/*
 * Singly-linked List access methods.
 */
#define SLIST_FIRST(head) ((head)->slh_first)
#define SLIST_END(head) NULL
#define SLIST_EMPTY(head) ((head)->slh_first == NULL)
#define SLIST_NEXT(elm, field) ((elm)->field.sle_next)

#define SLIST_FOREACH(var, head, field)                                                            \
    for ((var) = (head)->slh_first; (var) != SLIST_END(head); (var) = (var)->field.sle_next)

#define SLIST_FOREACH_SAFE(var, head, field, tvar)                                                 \
    for ((var) = SLIST_FIRST((head));                                                              \
         (var) != SLIST_END(head) && ((tvar) = SLIST_NEXT((var), field), 1); (var) = (tvar))

/*
 * Singly-linked List functions.
 */
#define SLIST_INIT(head)                                                                           \
    do {                                                                                           \
        (head)->slh_first = SLIST_END(head);                                                       \
    } while (/*CONSTCOND*/ 0)

#define SLIST_INSERT_AFTER(slistelm, elm, field)                                                   \
    do {                                                                                           \
        (elm)->field.sle_next = (slistelm)->field.sle_next;                                        \
        (slistelm)->field.sle_next = (elm);                                                        \
    } while (/*CONSTCOND*/ 0)

#define SLIST_INSERT_HEAD(head, elm, field)                                                        \
    do {                                                                                           \
        (elm)->field.sle_next = (head)->slh_first;                                                 \
        (head)->slh_first = (elm);                                                                 \
    } while (/*CONSTCOND*/ 0)

#define SLIST_REMOVE_AFTER(slistelm, field)                                                        \
    do {                                                                                           \
        (slistelm)->field.sle_next = SLIST_NEXT(SLIST_NEXT((slistelm), field), field);             \
    } while (/*CONSTCOND*/ 0)

#define SLIST_REMOVE_HEAD(head, field)                                                             \
    do {                                                                                           \
        (head)->slh_first = (head)->slh_first->field.sle_next;                                     \
    } while (/*CONSTCOND*/ 0)

#define SLIST_REMOVE(head, elm, type, field)                                                       \
    do {                                                                                           \
        if ((head)->slh_first == (elm)) {                                                          \
            SLIST_REMOVE_HEAD((head), field);                                                      \
        } else {                                                                                   \
            struct type *curelm = (head)->slh_first;                                               \
            while (curelm->field.sle_next != (elm))                                                \
                curelm = curelm->field.sle_next;                                                   \
            curelm->field.sle_next = curelm->field.sle_next->field.sle_next;                       \
        }                                                                                          \
    } while (/*CONSTCOND*/ 0)

/*
 * List definitions.
 */
#define LIST_HEAD(name, type)                                                                      \
    struct name {                                                                                  \
        struct type *lh_first; /* first element */                                                 \
    }

#define LIST_HEAD_INITIALIZER(head)                                                                \
    {                                                                                              \
        NULL                                                                                       \
    }

#define LIST_ENTRY(type)                                                                           \
    struct {                                                                                       \
        struct type *le_next;  /* next element */                                                  \
        struct type **le_prev; /* address of previous next element */                              \
    }

/*
 * List access methods.
 */
#define LIST_FIRST(head) ((head)->lh_first)
#define LIST_END(head) NULL
#define LIST_EMPTY(head) ((head)->lh_first == LIST_END(head))
#define LIST_NEXT(elm, field) ((elm)->field.le_next)

#define LIST_FOREACH(var, head, field)                                                             \
    for ((var) = ((head)->lh_first); (var) != LIST_END(head); (var) = ((var)->field.le_next))

#define LIST_FOREACH_SAFE(var, head, field, tvar)                                                  \
    for ((var) = LIST_FIRST((head));                                                               \
         (var) != LIST_END(head) && ((tvar) = LIST_NEXT((var), field), 1); (var) = (tvar))

#define LIST_MOVE(head1, head2)                                                                    \
    do {                                                                                           \
        LIST_INIT((head2));                                                                        \
        if (!LIST_EMPTY((head1))) {                                                                \
            (head2)->lh_first = (head1)->lh_first;                                                 \
            LIST_INIT((head1));                                                                    \
        }                                                                                          \
    } while (/*CONSTCOND*/ 0)

/*
 * List functions.
 */
#if defined(QUEUEDEBUG)
#define QUEUEDEBUG_LIST_INSERT_HEAD(head, elm, field)                                              \
    if ((head)->lh_first && (head)->lh_first->field.le_prev != &(head)->lh_first)                  \
        QUEUEDEBUG_ABORT("LIST_INSERT_HEAD %p %s:%d", (head), __FILE__, __LINE__);
#define QUEUEDEBUG_LIST_OP(elm, field)                                                             \
    if ((elm)->field.le_next && (elm)->field.le_next->field.le_prev != &(elm)->field.le_next)      \
        QUEUEDEBUG_ABORT("LIST_* forw %p %s:%d", (elm), __FILE__, __LINE__);                       \
    if (*(elm)->field.le_prev != (elm))                                                            \
        QUEUEDEBUG_ABORT("LIST_* back %p %s:%d", (elm), __FILE__, __LINE__);
#define QUEUEDEBUG_LIST_POSTREMOVE(elm, field)                                                     \
    (elm)->field.le_next = (void *)1L;                                                             \
    (elm)->field.le_prev = (void *)1L;
#else
#define QUEUEDEBUG_LIST_INSERT_HEAD(head, elm, field)
#define QUEUEDEBUG_LIST_OP(elm, field)
#define QUEUEDEBUG_LIST_POSTREMOVE(elm, field)
#endif

#define LIST_INIT(head)                                                                            \
    do {                                                                                           \
        (head)->lh_first = LIST_END(head);                                                         \
    } while (/*CONSTCOND*/ 0)

#define LIST_INSERT_AFTER(listelm, elm, field)                                                     \
    do {                                                                                           \
        QUEUEDEBUG_LIST_OP((listelm), field)                                                       \
        if (((elm)->field.le_next = (listelm)->field.le_next) != LIST_END(head))                   \
            (listelm)->field.le_next->field.le_prev = &(elm)->field.le_next;                       \
        (listelm)->field.le_next = (elm);                                                          \
        (elm)->field.le_prev = &(listelm)->field.le_next;                                          \
    } while (/*CONSTCOND*/ 0)

#define LIST_INSERT_BEFORE(listelm, elm, field)                                                    \
    do {                                                                                           \
        QUEUEDEBUG_LIST_OP((listelm), field)                                                       \
        (elm)->field.le_prev = (listelm)->field.le_prev;                                           \
        (elm)->field.le_next = (listelm);                                                          \
        *(listelm)->field.le_prev = (elm);                                                         \
        (listelm)->field.le_prev = &(elm)->field.le_next;                                          \
    } while (/*CONSTCOND*/ 0)

#define LIST_INSERT_HEAD(head, elm, field)                                                         \
    do {                                                                                           \
        QUEUEDEBUG_LIST_INSERT_HEAD((head), (elm), field)                                          \
        if (((elm)->field.le_next = (head)->lh_first) != LIST_END(head))                           \
            (head)->lh_first->field.le_prev = &(elm)->field.le_next;                               \
        (head)->lh_first = (elm);                                                                  \
        (elm)->field.le_prev = &(head)->lh_first;                                                  \
    } while (/*CONSTCOND*/ 0)

#define LIST_REMOVE(elm, field)                                                                    \
    do {                                                                                           \
        QUEUEDEBUG_LIST_OP((elm), field)                                                           \
        if ((elm)->field.le_next != NULL)                                                          \
            (elm)->field.le_next->field.le_prev = (elm)->field.le_prev;                            \
        *(elm)->field.le_prev = (elm)->field.le_next;                                              \
        QUEUEDEBUG_LIST_POSTREMOVE((elm), field)                                                   \
    } while (/*CONSTCOND*/ 0)

#define LIST_REPLACE(elm, elm2, field)                                                             \
    do {                                                                                           \
        if (((elm2)->field.le_next = (elm)->field.le_next) != NULL)                                \
            (elm2)->field.le_next->field.le_prev = &(elm2)->field.le_next;                         \
        (elm2)->field.le_prev = (elm)->field.le_prev;                                              \
        *(elm2)->field.le_prev = (elm2);                                                           \
        QUEUEDEBUG_LIST_POSTREMOVE((elm), field)                                                   \
    } while (/*CONSTCOND*/ 0)

/*
 * Simple queue definitions.
 */
#define SIMPLEQ_HEAD(name, type)                                                                   \
    struct name {                                                                                  \
        struct type *sqh_first; /* first element */                                                \
        struct type **sqh_last; /* addr of last next element */                                    \
    }

#define SIMPLEQ_HEAD_INITIALIZER(head)                                                             \
    {                                                                                              \
        NULL, &(head).sqh_first                                                                    \
    }

#define SIMPLEQ_ENTRY(type)                                                                        \
    struct {                                                                                       \
        struct type *sqe_next; /* next element */                                                  \
    }

/*
 * Simple queue access methods.
 */
#define SIMPLEQ_FIRST(head) ((head)->sqh_first)
#define SIMPLEQ_END(head) NULL
#define SIMPLEQ_EMPTY(head) ((head)->sqh_first == SIMPLEQ_END(head))
#define SIMPLEQ_NEXT(elm, field) ((elm)->field.sqe_next)

#define SIMPLEQ_FOREACH(var, head, field)                                                          \
    for ((var) = ((head)->sqh_first); (var) != SIMPLEQ_END(head); (var) = ((var)->field.sqe_next))

#define SIMPLEQ_FOREACH_SAFE(var, head, field, next)                                               \
    for ((var) = ((head)->sqh_first);                                                              \
         (var) != SIMPLEQ_END(head) && ((next = ((var)->field.sqe_next)), 1); (var) = (next))

/*
 * Simple queue functions.
 */
#define SIMPLEQ_INIT(head)                                                                         \
    do {                                                                                           \
        (head)->sqh_first = NULL;                                                                  \
        (head)->sqh_last = &(head)->sqh_first;                                                     \
    } while (/*CONSTCOND*/ 0)

#define SIMPLEQ_INSERT_HEAD(head, elm, field)                                                      \
    do {                                                                                           \
        if (((elm)->field.sqe_next = (head)->sqh_first) == NULL)                                   \
            (head)->sqh_last = &(elm)->field.sqe_next;                                             \
        (head)->sqh_first = (elm);                                                                 \
    } while (/*CONSTCOND*/ 0)

#define SIMPLEQ_INSERT_TAIL(head, elm, field)                                                      \
    do {                                                                                           \
        (elm)->field.sqe_next = NULL;                                                              \
        *(head)->sqh_last = (elm);                                                                 \
        (head)->sqh_last = &(elm)->field.sqe_next;                                                 \
    } while (/*CONSTCOND*/ 0)

#define SIMPLEQ_INSERT_AFTER(head, listelm, elm, field)                                            \
    do {                                                                                           \
        if (((elm)->field.sqe_next = (listelm)->field.sqe_next) == NULL)                           \
            (head)->sqh_last = &(elm)->field.sqe_next;                                             \
        (listelm)->field.sqe_next = (elm);                                                         \
    } while (/*CONSTCOND*/ 0)

#define SIMPLEQ_REMOVE_HEAD(head, field)                                                           \
    do {                                                                                           \
        if (((head)->sqh_first = (head)->sqh_first->field.sqe_next) == NULL)                       \
            (head)->sqh_last = &(head)->sqh_first;                                                 \
    } while (/*CONSTCOND*/ 0)

#define SIMPLEQ_REMOVE_AFTER(head, elm, field)                                                     \
    do {                                                                                           \
        if (((elm)->field.sqe_next = (elm)->field.sqe_next->field.sqe_next) == NULL)               \
            (head)->sqh_last = &(elm)->field.sqe_next;                                             \
    } while (/*CONSTCOND*/ 0)

#define SIMPLEQ_REMOVE(head, elm, type, field)                                                     \
    do {                                                                                           \
        if ((head)->sqh_first == (elm)) {                                                          \
            SIMPLEQ_REMOVE_HEAD((head), field);                                                    \
        } else {                                                                                   \
            struct type *curelm = (head)->sqh_first;                                               \
            while (curelm->field.sqe_next != (elm))                                                \
                curelm = curelm->field.sqe_next;                                                   \
            if ((curelm->field.sqe_next = curelm->field.sqe_next->field.sqe_next) == NULL)         \
                (head)->sqh_last = &(curelm)->field.sqe_next;                                      \
        }                                                                                          \
    } while (/*CONSTCOND*/ 0)

#define SIMPLEQ_CONCAT(head1, head2)                                                               \
    do {                                                                                           \
        if (!SIMPLEQ_EMPTY((head2))) {                                                             \
            *(head1)->sqh_last = (head2)->sqh_first;                                               \
            (head1)->sqh_last = (head2)->sqh_last;                                                 \
            SIMPLEQ_INIT((head2));                                                                 \
        }                                                                                          \
    } while (/*CONSTCOND*/ 0)

#define SIMPLEQ_LAST(head, type, field)                                                            \
    (SIMPLEQ_EMPTY((head))                                                                         \
         ? NULL                                                                                    \
         : ((struct type *)(void *)((char *)((head)->sqh_last) - offsetof(struct type, field))))

/*
 * Tail queue definitions.
 */
#define _TAILQ_HEAD(name, type, qual)                                                              \
    struct name {                                                                                  \
        qual type *tqh_first;      /* first element */                                             \
        qual type *qual *tqh_last; /* addr of last next element */                                 \
    }
#define TAILQ_HEAD(name, type) _TAILQ_HEAD(name, struct type, )

#define TAILQ_HEAD_INITIALIZER(head)                                                               \
    {                                                                                              \
        TAILQ_END(head), &(head).tqh_first                                                         \
    }

#define _TAILQ_ENTRY(type, qual)                                                                   \
    struct {                                                                                       \
        qual type *tqe_next;       /* next element */                                              \
        qual type *qual *tqe_prev; /* address of previous next element */                          \
    }
#define TAILQ_ENTRY(type) _TAILQ_ENTRY(struct type, )

/*
 * Tail queue access methods.
 */
#define TAILQ_FIRST(head) ((head)->tqh_first)
#define TAILQ_END(head) (NULL)
#define TAILQ_NEXT(elm, field) ((elm)->field.tqe_next)
#define TAILQ_LAST(head, headname) (*(((struct headname *)(void *)((head)->tqh_last))->tqh_last))
#define TAILQ_PREV(elm, headname, field)                                                           \
    (*(((struct headname *)(void *)((elm)->field.tqe_prev))->tqh_last))
#define TAILQ_EMPTY(head) (TAILQ_FIRST(head) == TAILQ_END(head))

#define TAILQ_FOREACH(var, head, field)                                                            \
    for ((var) = ((head)->tqh_first); (var) != TAILQ_END(head); (var) = ((var)->field.tqe_next))

#define TAILQ_FOREACH_SAFE(var, head, field, next)                                                 \
    for ((var) = ((head)->tqh_first);                                                              \
         (var) != TAILQ_END(head) && ((next) = TAILQ_NEXT(var, field), 1); (var) = (next))

#define TAILQ_FOREACH_REVERSE(var, head, headname, field)                                          \
    for ((var) = TAILQ_LAST((head), headname); (var) != TAILQ_END(head);                           \
         (var) = TAILQ_PREV((var), headname, field))

#define TAILQ_FOREACH_REVERSE_SAFE(var, head, headname, field, prev)                               \
    for ((var) = TAILQ_LAST((head), headname);                                                     \
         (var) != TAILQ_END(head) && ((prev) = TAILQ_PREV((var), headname, field), 1);             \
         (var) = (prev))

/*
 * Tail queue functions.
 */
#if defined(QUEUEDEBUG)
#define QUEUEDEBUG_TAILQ_INSERT_HEAD(head, elm, field)                                             \
    if ((head)->tqh_first && (head)->tqh_first->field.tqe_prev != &(head)->tqh_first)              \
        QUEUEDEBUG_ABORT("TAILQ_INSERT_HEAD %p %s:%d", (head), __FILE__, __LINE__);
#define QUEUEDEBUG_TAILQ_INSERT_TAIL(head, elm, field)                                             \
    if (*(head)->tqh_last != NULL)                                                                 \
        QUEUEDEBUG_ABORT("TAILQ_INSERT_TAIL %p %s:%d", (head), __FILE__, __LINE__);
#define QUEUEDEBUG_TAILQ_OP(elm, field)                                                            \
    if ((elm)->field.tqe_next && (elm)->field.tqe_next->field.tqe_prev != &(elm)->field.tqe_next)  \
        QUEUEDEBUG_ABORT("TAILQ_* forw %p %s:%d", (elm), __FILE__, __LINE__);                      \
    if (*(elm)->field.tqe_prev != (elm))                                                           \
        QUEUEDEBUG_ABORT("TAILQ_* back %p %s:%d", (elm), __FILE__, __LINE__);
#define QUEUEDEBUG_TAILQ_PREREMOVE(head, elm, field)                                               \
    if ((elm)->field.tqe_next == NULL && (head)->tqh_last != &(elm)->field.tqe_next)               \
        QUEUEDEBUG_ABORT("TAILQ_PREREMOVE head %p elm %p %s:%d", (head), (elm), __FILE__, __LINE__);
#define QUEUEDEBUG_TAILQ_POSTREMOVE(elm, field)                                                    \
    (elm)->field.tqe_next = (void *)1L;                                                            \
    (elm)->field.tqe_prev = (void *)1L;
#else
#define QUEUEDEBUG_TAILQ_INSERT_HEAD(head, elm, field)
#define QUEUEDEBUG_TAILQ_INSERT_TAIL(head, elm, field)
#define QUEUEDEBUG_TAILQ_OP(elm, field)
#define QUEUEDEBUG_TAILQ_PREREMOVE(head, elm, field)
#define QUEUEDEBUG_TAILQ_POSTREMOVE(elm, field)
#endif

#define TAILQ_INIT(head)                                                                           \
    do {                                                                                           \
        (head)->tqh_first = TAILQ_END(head);                                                       \
        (head)->tqh_last = &(head)->tqh_first;                                                     \
    } while (/*CONSTCOND*/ 0)

#define TAILQ_INSERT_HEAD(head, elm, field)                                                        \
    do {                                                                                           \
        QUEUEDEBUG_TAILQ_INSERT_HEAD((head), (elm), field)                                         \
        if (((elm)->field.tqe_next = (head)->tqh_first) != TAILQ_END(head))                        \
            (head)->tqh_first->field.tqe_prev = &(elm)->field.tqe_next;                            \
        else                                                                                       \
            (head)->tqh_last = &(elm)->field.tqe_next;                                             \
        (head)->tqh_first = (elm);                                                                 \
        (elm)->field.tqe_prev = &(head)->tqh_first;                                                \
    } while (/*CONSTCOND*/ 0)

#define TAILQ_INSERT_TAIL(head, elm, field)                                                        \
    do {                                                                                           \
        QUEUEDEBUG_TAILQ_INSERT_TAIL((head), (elm), field)                                         \
        (elm)->field.tqe_next = TAILQ_END(head);                                                   \
        (elm)->field.tqe_prev = (head)->tqh_last;                                                  \
        *(head)->tqh_last = (elm);                                                                 \
        (head)->tqh_last = &(elm)->field.tqe_next;                                                 \
    } while (/*CONSTCOND*/ 0)

#define TAILQ_INSERT_AFTER(head, listelm, elm, field)                                              \
    do {                                                                                           \
        QUEUEDEBUG_TAILQ_OP((listelm), field)                                                      \
        if (((elm)->field.tqe_next = (listelm)->field.tqe_next) != TAILQ_END(head))                \
            (elm)->field.tqe_next->field.tqe_prev = &(elm)->field.tqe_next;                        \
        else                                                                                       \
            (head)->tqh_last = &(elm)->field.tqe_next;                                             \
        (listelm)->field.tqe_next = (elm);                                                         \
        (elm)->field.tqe_prev = &(listelm)->field.tqe_next;                                        \
    } while (/*CONSTCOND*/ 0)

#define TAILQ_INSERT_BEFORE(listelm, elm, field)                                                   \
    do {                                                                                           \
        QUEUEDEBUG_TAILQ_OP((listelm), field)                                                      \
        (elm)->field.tqe_prev = (listelm)->field.tqe_prev;                                         \
        (elm)->field.tqe_next = (listelm);                                                         \
        *(listelm)->field.tqe_prev = (elm);                                                        \
        (listelm)->field.tqe_prev = &(elm)->field.tqe_next;                                        \
    } while (/*CONSTCOND*/ 0)

#define TAILQ_REMOVE(head, elm, field)                                                             \
    do {                                                                                           \
        QUEUEDEBUG_TAILQ_PREREMOVE((head), (elm), field)                                           \
        QUEUEDEBUG_TAILQ_OP((elm), field)                                                          \
        if (((elm)->field.tqe_next) != TAILQ_END(head))                                            \
            (elm)->field.tqe_next->field.tqe_prev = (elm)->field.tqe_prev;                         \
        else                                                                                       \
            (head)->tqh_last = (elm)->field.tqe_prev;                                              \
        *(elm)->field.tqe_prev = (elm)->field.tqe_next;                                            \
        QUEUEDEBUG_TAILQ_POSTREMOVE((elm), field);                                                 \
    } while (/*CONSTCOND*/ 0)

#define TAILQ_REPLACE(head, elm, elm2, field)                                                      \
    do {                                                                                           \
        if (((elm2)->field.tqe_next = (elm)->field.tqe_next) != TAILQ_END(head))                   \
            (elm2)->field.tqe_next->field.tqe_prev = &(elm2)->field.tqe_next;                      \
        else                                                                                       \
            (head)->tqh_last = &(elm2)->field.tqe_next;                                            \
        (elm2)->field.tqe_prev = (elm)->field.tqe_prev;                                            \
        *(elm2)->field.tqe_prev = (elm2);                                                          \
        QUEUEDEBUG_TAILQ_POSTREMOVE((elm), field);                                                 \
    } while (/*CONSTCOND*/ 0)

#define TAILQ_CONCAT(head1, head2, field)                                                          \
    do {                                                                                           \
        if (!TAILQ_EMPTY(head2)) {                                                                 \
            *(head1)->tqh_last = (head2)->tqh_first;                                               \
            (head2)->tqh_first->field.tqe_prev = (head1)->tqh_last;                                \
            (head1)->tqh_last = (head2)->tqh_last;                                                 \
            TAILQ_INIT((head2));                                                                   \
        }                                                                                          \
    } while (/*CONSTCOND*/ 0)

/*
 * Singly-linked Tail queue declarations.
 */
#define STAILQ_HEAD(name, type)                                                                    \
    struct name {                                                                                  \
        struct type *stqh_first; /* first element */                                               \
        struct type **stqh_last; /* addr of last next element */                                   \
    }

#define STAILQ_HEAD_INITIALIZER(head)                                                              \
    {                                                                                              \
        NULL, &(head).stqh_first                                                                   \
    }

#define STAILQ_ENTRY(type)                                                                         \
    struct {                                                                                       \
        struct type *stqe_next; /* next element */                                                 \
    }

/*
 * Singly-linked Tail queue access methods.
 */
#define STAILQ_FIRST(head) ((head)->stqh_first)
#define STAILQ_END(head) NULL
#define STAILQ_NEXT(elm, field) ((elm)->field.stqe_next)
#define STAILQ_EMPTY(head) (STAILQ_FIRST(head) == STAILQ_END(head))

/*
 * Singly-linked Tail queue functions.
 */
#define STAILQ_INIT(head)                                                                          \
    do {                                                                                           \
        (head)->stqh_first = NULL;                                                                 \
        (head)->stqh_last = &(head)->stqh_first;                                                   \
    } while (/*CONSTCOND*/ 0)

#define STAILQ_INSERT_HEAD(head, elm, field)                                                       \
    do {                                                                                           \
        if (((elm)->field.stqe_next = (head)->stqh_first) == NULL)                                 \
            (head)->stqh_last = &(elm)->field.stqe_next;                                           \
        (head)->stqh_first = (elm);                                                                \
    } while (/*CONSTCOND*/ 0)

#define STAILQ_INSERT_TAIL(head, elm, field)                                                       \
    do {                                                                                           \
        (elm)->field.stqe_next = NULL;                                                             \
        *(head)->stqh_last = (elm);                                                                \
        (head)->stqh_last = &(elm)->field.stqe_next;                                               \
    } while (/*CONSTCOND*/ 0)

#define STAILQ_INSERT_AFTER(head, listelm, elm, field)                                             \
    do {                                                                                           \
        if (((elm)->field.stqe_next = (listelm)->field.stqe_next) == NULL)                         \
            (head)->stqh_last = &(elm)->field.stqe_next;                                           \
        (listelm)->field.stqe_next = (elm);                                                        \
    } while (/*CONSTCOND*/ 0)

#define STAILQ_REMOVE_HEAD(head, field)                                                            \
    do {                                                                                           \
        if (((head)->stqh_first = (head)->stqh_first->field.stqe_next) == NULL)                    \
            (head)->stqh_last = &(head)->stqh_first;                                               \
    } while (/*CONSTCOND*/ 0)

#define STAILQ_REMOVE(head, elm, type, field)                                                      \
    do {                                                                                           \
        if ((head)->stqh_first == (elm)) {                                                         \
            STAILQ_REMOVE_HEAD((head), field);                                                     \
        } else {                                                                                   \
            struct type *curelm = (head)->stqh_first;                                              \
            while (curelm->field.stqe_next != (elm))                                               \
                curelm = curelm->field.stqe_next;                                                  \
            if ((curelm->field.stqe_next = curelm->field.stqe_next->field.stqe_next) == NULL)      \
                (head)->stqh_last = &(curelm)->field.stqe_next;                                    \
        }                                                                                          \
    } while (/*CONSTCOND*/ 0)

#define STAILQ_FOREACH(var, head, field)                                                           \
    for ((var) = ((head)->stqh_first); (var); (var) = ((var)->field.stqe_next))

#define STAILQ_FOREACH_SAFE(var, head, field, tvar)                                                \
    for ((var) = STAILQ_FIRST((head)); (var) && ((tvar) = STAILQ_NEXT((var), field), 1);           \
         (var) = (tvar))

#define STAILQ_CONCAT(head1, head2)                                                                \
    do {                                                                                           \
        if (!STAILQ_EMPTY((head2))) {                                                              \
            *(head1)->stqh_last = (head2)->stqh_first;                                             \
            (head1)->stqh_last = (head2)->stqh_last;                                               \
            STAILQ_INIT((head2));                                                                  \
        }                                                                                          \
    } while (/*CONSTCOND*/ 0)

#define STAILQ_LAST(head, type, field)                                                             \
    (STAILQ_EMPTY((head))                                                                          \
         ? NULL                                                                                    \
         : ((struct type *)(void *)((char *)((head)->stqh_last) - offsetof(struct type, field))))

#if 0
/*
 * Circular queue definitions. Do not use. We still keep the macros
 * for compatibility but because of pointer aliasing issues their use
 * is discouraged!
 */

/*
 * __launder_type():  We use this ugly hack to work around the the compiler
 * noticing that two types may not alias each other and elide tests in code.
 * We hit this in the CIRCLEQ macros when comparing 'struct name *' and
 * 'struct type *' (see CIRCLEQ_HEAD()).  Modern compilers (such as GCC
 * 4.8) declare these comparisons as always false, causing the code to
 * not run as designed.
 *
 * This hack is only to be used for comparisons and thus can be fully const.
 * Do not use for assignment.
 *
 * If we ever choose to change the ABI of the CIRCLEQ macros, we could fix
 * this by changing the head/tail sentinal values, but see the note above
 * this one.
 */
static __inline const void * __launder_type(const void *);
static __inline const void *
__launder_type(const void *__x)
{
	__asm __volatile("" : "+r" (__x));
	return __x;
}

#if defined(QUEUEDEBUG)
#define QUEUEDEBUG_CIRCLEQ_HEAD(head, field)                                                       \
    if ((head)->cqh_first != CIRCLEQ_ENDC(head) &&                                                 \
        (head)->cqh_first->field.cqe_prev != CIRCLEQ_ENDC(head))                                   \
        QUEUEDEBUG_ABORT("CIRCLEQ head forw %p %s:%d", (head), __FILE__, __LINE__);                \
    if ((head)->cqh_last != CIRCLEQ_ENDC(head) &&                                                  \
        (head)->cqh_last->field.cqe_next != CIRCLEQ_ENDC(head))                                    \
        QUEUEDEBUG_ABORT("CIRCLEQ head back %p %s:%d", (head), __FILE__, __LINE__);
#define QUEUEDEBUG_CIRCLEQ_ELM(head, elm, field)                                                   \
    if ((elm)->field.cqe_next == CIRCLEQ_ENDC(head)) {                                             \
        if ((head)->cqh_last != (elm))                                                             \
            QUEUEDEBUG_ABORT("CIRCLEQ elm last %p %s:%d", (elm), __FILE__, __LINE__);              \
    } else {                                                                                       \
        if ((elm)->field.cqe_next->field.cqe_prev != (elm))                                        \
            QUEUEDEBUG_ABORT("CIRCLEQ elm forw %p %s:%d", (elm), __FILE__, __LINE__);              \
    }                                                                                              \
    if ((elm)->field.cqe_prev == CIRCLEQ_ENDC(head)) {                                             \
        if ((head)->cqh_first != (elm))                                                            \
            QUEUEDEBUG_ABORT("CIRCLEQ elm first %p %s:%d", (elm), __FILE__, __LINE__);             \
    } else {                                                                                       \
        if ((elm)->field.cqe_prev->field.cqe_next != (elm))                                        \
            QUEUEDEBUG_ABORT("CIRCLEQ elm prev %p %s:%d", (elm), __FILE__, __LINE__);              \
    }
#define QUEUEDEBUG_CIRCLEQ_POSTREMOVE(elm, field)                                                  \
    (elm)->field.cqe_next = (void *)1L;                                                            \
    (elm)->field.cqe_prev = (void *)1L;
#else
#define QUEUEDEBUG_CIRCLEQ_HEAD(head, field)
#define QUEUEDEBUG_CIRCLEQ_ELM(head, elm, field)
#define QUEUEDEBUG_CIRCLEQ_POSTREMOVE(elm, field)
#endif

#define CIRCLEQ_HEAD(name, type)                                                                   \
    struct name {                                                                                  \
        struct type *cqh_first; /* first element */                                                \
        struct type *cqh_last;  /* last element */                                                 \
    }

#define CIRCLEQ_HEAD_INITIALIZER(head)                                                             \
    {                                                                                              \
        CIRCLEQ_END(&head), CIRCLEQ_END(&head)                                                     \
    }

#define CIRCLEQ_ENTRY(type)                                                                        \
    struct {                                                                                       \
        struct type *cqe_next; /* next element */                                                  \
        struct type *cqe_prev; /* previous element */                                              \
    }

/*
 * Circular queue functions.
 */
#define CIRCLEQ_INIT(head)                                                                         \
    do {                                                                                           \
        (head)->cqh_first = CIRCLEQ_END(head);                                                     \
        (head)->cqh_last = CIRCLEQ_END(head);                                                      \
    } while (/*CONSTCOND*/ 0)

#define CIRCLEQ_INSERT_AFTER(head, listelm, elm, field)                                            \
    do {                                                                                           \
        QUEUEDEBUG_CIRCLEQ_HEAD((head), field)                                                     \
        QUEUEDEBUG_CIRCLEQ_ELM((head), (listelm), field)                                           \
        (elm)->field.cqe_next = (listelm)->field.cqe_next;                                         \
        (elm)->field.cqe_prev = (listelm);                                                         \
        if ((listelm)->field.cqe_next == CIRCLEQ_ENDC(head))                                       \
            (head)->cqh_last = (elm);                                                              \
        else                                                                                       \
            (listelm)->field.cqe_next->field.cqe_prev = (elm);                                     \
        (listelm)->field.cqe_next = (elm);                                                         \
    } while (/*CONSTCOND*/ 0)

#define CIRCLEQ_INSERT_BEFORE(head, listelm, elm, field)                                           \
    do {                                                                                           \
        QUEUEDEBUG_CIRCLEQ_HEAD((head), field)                                                     \
        QUEUEDEBUG_CIRCLEQ_ELM((head), (listelm), field)                                           \
        (elm)->field.cqe_next = (listelm);                                                         \
        (elm)->field.cqe_prev = (listelm)->field.cqe_prev;                                         \
        if ((listelm)->field.cqe_prev == CIRCLEQ_ENDC(head))                                       \
            (head)->cqh_first = (elm);                                                             \
        else                                                                                       \
            (listelm)->field.cqe_prev->field.cqe_next = (elm);                                     \
        (listelm)->field.cqe_prev = (elm);                                                         \
    } while (/*CONSTCOND*/ 0)

#define CIRCLEQ_INSERT_HEAD(head, elm, field)                                                      \
    do {                                                                                           \
        QUEUEDEBUG_CIRCLEQ_HEAD((head), field)                                                     \
        (elm)->field.cqe_next = (head)->cqh_first;                                                 \
        (elm)->field.cqe_prev = CIRCLEQ_END(head);                                                 \
        if ((head)->cqh_last == CIRCLEQ_ENDC(head))                                                \
            (head)->cqh_last = (elm);                                                              \
        else                                                                                       \
            (head)->cqh_first->field.cqe_prev = (elm);                                             \
        (head)->cqh_first = (elm);                                                                 \
    } while (/*CONSTCOND*/ 0)

#define CIRCLEQ_INSERT_TAIL(head, elm, field)                                                      \
    do {                                                                                           \
        QUEUEDEBUG_CIRCLEQ_HEAD((head), field)                                                     \
        (elm)->field.cqe_next = CIRCLEQ_END(head);                                                 \
        (elm)->field.cqe_prev = (head)->cqh_last;                                                  \
        if ((head)->cqh_first == CIRCLEQ_ENDC(head))                                               \
            (head)->cqh_first = (elm);                                                             \
        else                                                                                       \
            (head)->cqh_last->field.cqe_next = (elm);                                              \
        (head)->cqh_last = (elm);                                                                  \
    } while (/*CONSTCOND*/ 0)

#define CIRCLEQ_REMOVE(head, elm, field)                                                           \
    do {                                                                                           \
        QUEUEDEBUG_CIRCLEQ_HEAD((head), field)                                                     \
        QUEUEDEBUG_CIRCLEQ_ELM((head), (elm), field)                                               \
        if ((elm)->field.cqe_next == CIRCLEQ_ENDC(head))                                           \
            (head)->cqh_last = (elm)->field.cqe_prev;                                              \
        else                                                                                       \
            (elm)->field.cqe_next->field.cqe_prev = (elm)->field.cqe_prev;                         \
        if ((elm)->field.cqe_prev == CIRCLEQ_ENDC(head))                                           \
            (head)->cqh_first = (elm)->field.cqe_next;                                             \
        else                                                                                       \
            (elm)->field.cqe_prev->field.cqe_next = (elm)->field.cqe_next;                         \
        QUEUEDEBUG_CIRCLEQ_POSTREMOVE((elm), field)                                                \
    } while (/*CONSTCOND*/ 0)

#define CIRCLEQ_FOREACH(var, head, field)                                                          \
    for ((var) = ((head)->cqh_first); (var) != CIRCLEQ_ENDC(head); (var) = ((var)->field.cqe_next))

#define CIRCLEQ_FOREACH_REVERSE(var, head, field)                                                  \
    for ((var) = ((head)->cqh_last); (var) != CIRCLEQ_ENDC(head); (var) = ((var)->field.cqe_prev))

/*
 * Circular queue access methods.
 */
#define CIRCLEQ_FIRST(head) ((head)->cqh_first)
#define CIRCLEQ_LAST(head) ((head)->cqh_last)
/* For comparisons */
#define CIRCLEQ_ENDC(head) (__launder_type(head))
/* For assignments */
#define CIRCLEQ_END(head) ((void *)(head))
#define CIRCLEQ_NEXT(elm, field) ((elm)->field.cqe_next)
#define CIRCLEQ_PREV(elm, field) ((elm)->field.cqe_prev)
#define CIRCLEQ_EMPTY(head) (CIRCLEQ_FIRST(head) == CIRCLEQ_ENDC(head))

#define CIRCLEQ_LOOP_NEXT(head, elm, field)                                                        \
    (((elm)->field.cqe_next == CIRCLEQ_ENDC(head)) ? ((head)->cqh_first) : (elm->field.cqe_next))
#define CIRCLEQ_LOOP_PREV(head, elm, field)                                                        \
    (((elm)->field.cqe_prev == CIRCLEQ_ENDC(head)) ? ((head)->cqh_last) : (elm->field.cqe_prev))
#endif
